Osteoarthritis (OA) is a painful, non-inflammatory disorder of the joints that involves the degeneration of cartilage and the formation of osteophytes and is strongly associated with aging. Caloric restriction (CR) has proven to be a useful technique to slow aging in smaller animals; consequently, research into CR in non-human primates (NHP), where OA seems to be ubiquitous, is ongoing. Macaque monkeys, the focus of much CR research, exhibit a high prevalence of OA, and therefore represent an excellent model in which to test the hypothesis that, by slowing the aging process, CR slows the development and progression of OA. We will evaluate OA in spinal and peripheral joints using radiographic signs of the degeneration of cartilage and the formation of osteophytes in control and CR groups of rhesus macaques that are part of a long-term CR project. We aim to establish the effects of CR on the development and progression of OA using cross-sectional and longitudinal approaches. Radiographs of the complete spine and major peripheral joints will be scored using an atlas method Io establish the presence of joint space narrowing, osteophytosis, and the condition of the joint surface. Serial radiographs will allow us to develop the rate of change in average score. Average score for each OA marker and the rate of change in score will be compared between the dietary groups.